1. Field of the Invention
The present invention relates to a rotor assembly, and more particularly to a fan rotor assembly having an inner rotor and an outer rotor and each of the inner and outer rotors has multiple blades to provide two sets of blades and therefore to supply excellent airflow.
2. Description of Related Art
Fans are used in electronic devices to dissipate heat from electronic components such as chips inside the electronic devices. A conventional fan rotor of a fan is formed integrally into one piece, is made of plastic by injection molding process and has multiple blades formed radially on the fan rotor. Because the electronic devices are designed more and more compact, fans mounted in the electronic devices have to be sized smaller and smaller with the plastic blades becomes thinner and thinner. However, the thinned plastic blades are too weak and fragile to bear high air pressure and easily snap when the fan rotor rotates.
To overcome the snaps of the thinned plastic blades on the small fan rotor, a metal fan rotor has been developed. The metal fan rotor is made of a metal sheet by stamping the metal sheet and has metal blades. However, the stamping process restricts the a total number of the metal blades formed on the metal fan rotor to be less than that of the plastic blades of the conventional plastic fan rotor. Therefore, the metal fan rotor with less metal blades produces insufficient airflow less than that produced by the plastic fan rotor with more plastic blades. Accordingly, the metal fan rotor has a disappointing heat-dissipating performance.
To overcome the shortcomings, the present invention provides a fan rotor assembly to mitigate or obviate the aforementioned problems.